Virtual Router Redundancy Protocol (VRRP) is a redundancy protocol described in Request for Comments (RFC) 3768 that is designed to increase the availability of a default gateway servicing hosts on the same subnet. This increased reliability is achieved by advertising a “virtual router” (an abstract representation of master and backup routers acting as a group) as a default gateway to the host(s) instead of one physical router. Two or more physical routers are then configured to stand for the virtual router, with only one doing the actual routing at any given time. If the current physical router that is routing the data on behalf of the virtual router fails, an arrangement is made for another physical router to automatically replace it. The physical router that is currently forwarding data on behalf of the virtual router is called the master router. Physical routers standing by to take over from the master router in case something goes wrong are called backup routers.
In VRRP, there is one Owner and one or more Backups for each virtual router. The Owner is the router that has the Internet Protocol (IP) address used for the virtual router. All the other routers supporting the virtual router are backups.
VRRP can be used over Ethernet, Multiprotocol Label Switching (MPLS), and token ring networks. VRRP provides information on the state of a router, not the routes processed and exchanged by that router. Each VRRP instance is limited in scope to a single subnet. It does not advertise Internet Protocol (IP) routes beyond that subnet or affect the routing table in any way.
VRRP-E is a proprietary version of VRPP offered by Brocade Communications Systems, Inc. of San Jose, Calif. Unlike VRRP, VRRP-E does not use Owners. All VRRP-E routers are Backups for a given virtual router. The router with the highest priority becomes the Master.
In existing VRRP and VRRP-E implementations, the data traffic sometimes needs to cross a wide area network (WAN) interface twice before it is forwarded towards the final destination. For example, traffic received by the backup router that needs to be sent through interfaces on the backup router to reach the final destination is first switched to the master router from the backup router, and then forwarded back to the backup router, where it is forwarded towards the final destination. This behavior can result in high packet forwarding times, inefficient WAN bandwidth utilization, and degraded router performance.
VMware ESX is an enterprise-level virtualization product offered by VMware, Inc. VMware ESX Server is a thin software layer designed to multiplex hardware resources efficiently among virtual machines running unmodified commodity operating systems. The basic server requires some form of persistent storage—typically, an array of hard disk drives—for storing the virtualization kernel and support files.
In server virtualization environments, there are typically many virtual servers that are configured to dynamically move between different VMware ESX servers connected by WAN links. Since each time a virtual server is activated it can be on different ESX, the behavior described above where traffic needs to cross the WAN twice before it reaches the client can occur frequently.
In a Gateway Load Balancing Protocol (GLBP) solution, the traffic from different servers can be load shared among different routers. However, all the traffic from a particular router will still be forwarded using the same gateway router. Therefore, a GLBP solution cannot be effectively used to address the problem of dynamically-moving virtual servers. Accordingly, a need exists in the art for an improved solution for virtual router redundancy for server virtualization.